From f617842dae7b8c9d6a0f1c503299ecfdd1ef5503 Mon Sep 17 00:00:00 2001
From: chloe caruso <git@paperclover.net>
Date: Sun, 4 May 2025 08:42:28 -0700
Subject: [PATCH] initial commit

---
 .gitignore |  2 ++
 boot.s     | 28 +++++++++++++++++++++
 build.zig  | 32 ++++++++++++++++++++++++
 grub.cfg   |  3 +++
 kernel.zig | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 linker.ld  | 23 ++++++++++++++++++
 6 files changed, 159 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 boot.s
 create mode 100644 build.zig
 create mode 100644 grub.cfg
 create mode 100644 kernel.zig
 create mode 100644 linker.ld

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..d8c8979
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+.zig-cache
+zig-out
diff --git a/boot.s b/boot.s
new file mode 100644
index 0000000..ea9f682
--- /dev/null
+++ b/boot.s
@@ -0,0 +1,28 @@
+.section .multiboot
+    .align 4
+    .set ALIGN, 1<<0
+    .set MEMINFO, 1<<1
+    .set MAGIC, 0x1BADB002
+    .set FLAGS, ALIGN|MEMINFO
+    .long MAGIC
+    .long FLAGS
+    .long -(MAGIC + FLAGS)
+
+.section .bss
+    .align 16
+stack_bottom:
+    .skip 16384
+stack_top:
+
+.section .text
+.global _start
+.type _start, @function
+_start:
+    mov $stack_top, %esp
+
+    call kernel_main
+
+    cli
+1:  hlt
+    jmp 1b
+.size _start, . - _start
\ No newline at end of file
diff --git a/build.zig b/build.zig
new file mode 100644
index 0000000..e33626d
--- /dev/null
+++ b/build.zig
@@ -0,0 +1,32 @@
+pub fn build(b: *Build) !void {
+    const optimize = std.builtin.OptimizeMode.Debug;
+    const target = b.resolveTargetQuery(.{
+        .cpu_arch = .x86,
+        .os_tag = .freestanding,
+        .abi = .none,
+    });
+    const exe = b.addExecutable(.{
+        .root_source_file = b.path("kernel.zig"),
+        .name = "multiboot",
+        .target = target,
+        .optimize = optimize,
+    });
+    exe.addCSourceFile(.{
+        .file = b.path("boot.s"),
+    });
+    exe.setLinkerScript(b.path("linker.ld"));
+
+    const iso_dir = b.addWriteFiles();
+    _ = iso_dir.addCopyFile(exe.getEmittedBin(), "boot/os.bin");
+    _ = iso_dir.addCopyFile(b.path("grub.cfg"), "boot/grub/grub.cfg");
+    const make_iso = b.addSystemCommand(&.{"i686-elf-grub-mkrescue"});
+    make_iso.addArg("-o");
+    const iso = make_iso.addOutputFileArg("lab.iso");
+    make_iso.addDirectoryArg(iso_dir.getDirectory());
+
+    b.getInstallStep()
+        .dependOn(&b.addInstallFile(iso, "lab.iso").step);
+}
+
+const std = @import("std");
+const Build = std.Build;
diff --git a/grub.cfg b/grub.cfg
new file mode 100644
index 0000000..72c25b9
--- /dev/null
+++ b/grub.cfg
@@ -0,0 +1,3 @@
+menuentry "experiment" {
+    multiboot /boot/os.bin
+}
diff --git a/kernel.zig b/kernel.zig
new file mode 100644
index 0000000..cc45e68
--- /dev/null
+++ b/kernel.zig
@@ -0,0 +1,71 @@
+const vga = struct {
+    const width = 80;
+    const height = 25;
+    const screen: *[width * height]Cell = @ptrFromInt(0xB8000);
+
+    const Cell = packed struct(u16) {
+        char: u8,
+        style: Style = .default,
+
+        const blank: Cell = .{ .char = ' ' };
+    };
+
+    const Style = packed struct(u8) {
+        fg: Color,
+        bg: Color,
+
+        pub const default: Style = .{
+            .fg = .black,
+            .bg = .light_cyan,
+        };
+    };
+
+    const Color = enum(u4) {
+        black = 0,
+        blue = 1,
+        green = 2,
+        cyan = 3,
+        red = 4,
+        magenta = 5,
+        brown = 6,
+        light_grey = 7,
+        dark_grey = 8,
+        light_blue = 9,
+        light_green = 10,
+        light_cyan = 11,
+        light_red = 12,
+        light_magenta = 13,
+        light_brown = 14,
+        white = 15,
+    };
+
+    fn init() void {
+        @memset(screen, .blank);
+    }
+
+    fn set(x: u32, y: u32, cell: Cell) void {
+        screen[x + y * width] = cell;
+    }
+};
+
+var current_x: u32 = 0;
+var current_y: u32 = 0;
+
+fn writeString(slice: []const u8, style: vga.Style) void {
+    for (slice) |char| {
+        vga.set(current_x, current_y, .{ .char = char, .style = style });
+        current_x += 1;
+        if (current_x >= vga.width) {
+            current_x = 0;
+            current_y += 1;
+            if (current_y >= vga.height) {
+                current_y = 0;
+            }
+        }
+    }
+}
+
+export fn kernel_main() callconv(.c) void {
+    vga.init();
+    writeString("Hello Kernel", .default);
+}
diff --git a/linker.ld b/linker.ld
new file mode 100644
index 0000000..7593d7f
--- /dev/null
+++ b/linker.ld
@@ -0,0 +1,23 @@
+ENTRY(_start)
+SECTIONS
+{
+    . = 2M;
+    .text : ALIGN(4K)
+    {
+        *(.multiboot)
+        *(.text)
+    }
+    .rodata : ALIGN(4K)
+    {
+        *(.rodata)
+    }
+    .data : ALIGN(4K)
+    {
+        *(data)
+    }
+    .bss : ALIGN(4K)
+    {
+        *(COMMON)
+        *(.bss)
+    }
+}